Why Does My Hot Tub’s pH Keep Rising?

Rising pH levels can be caused by high alkalinity, aeration, or using certain chemicals. Lower the alkalinity first if needed, then use a pH decreaser to bring pH levels down.

What Is pH And Why Is It Important?

pH measures how acidic or basic your hot tub water is. The ideal range is between 7.2 and 7.8. When pH climbs above 7.8, water becomes too alkaline. This reduces the effectiveness of your sanitizer and increases the chances of scale buildup.

Balanced pH is essential for comfortable soaking and long-term hot tub care. If left unchecked, high pH can also shorten the life of filters, jets, and pumps.

Why Does pH Rise In Hot Tubs?

There are several reasons your hot tub’s pH may keep increasing:

• High alkalinity levels

• Poor water circulation

• Aeration from jets and bubblers

• Use of certain sanitizers

• Excessive body oils, lotions, and contaminants

• Frequent topping off with hard water

Each of these can gradually shift the water’s chemistry, pushing pH levels up over time.

High Total Alkalinity

Alkalinity acts as a buffer for pH. When it is too high, pH tends to rise with it.

• Ideal alkalinity: 80 to 120 ppm

• High alkalinity often leads to drifting or constantly high pH

Lowering your alkalinity will usually stabilize your pH.

Aeration And Jets

Hot tubs create lots of bubbles. While that makes for a relaxing soak, aeration can actually raise pH.

• Bubbling agitates carbon dioxide in the water

• As CO2 escapes, the pH naturally rises

This is especially true in tubs that run long jet cycles or have waterfalls and air blowers.

Hard Water And Minerals

If your local water supply is high in calcium or other minerals, it can push your pH up.

• Hard water usually comes with a high pH from the start

• Regularly topping off evaporated water can slowly increase your total pH

Water softeners or pre-filters may help reduce mineral buildup before it enters the tub.

Chemical Reactions From Sanitizers

Some sanitizers raise pH more than others:

• Dichlor and cal hypo (types of chlorine) both increase pH

• Bromine is more stable but still has a slight effect

• Biguanide and mineral systems have minimal impact

If you notice high pH after shocking or sanitizing, your choice of products may be contributing.

How Can I Prevent My pH From Rising?

Test Your Water Regularly

• Use test strips or a liquid kit 2 to 3 times per week

• Check pH, alkalinity, and sanitizer levels together

• Log your test results to track patterns over time

Frequent testing helps you catch rising pH early and make adjustments before it becomes a problem.

Lower Total Alkalinity First

Before adjusting pH directly, address your alkalinity. Use a pH decreaser (sodium bisulfate) to bring it within range.

Steps to lower alkalinity:

1. Measure current alkalinity levels

2. Add small amounts of pH decreaser

3. Run the jets for at least 30 minutes

4. Retest after a few hours and repeat if needed

Once alkalinity is balanced, pH is easier to control.

Use pH Down Products Sparingly

Adding pH decreaser can help, but overuse causes constant chasing.

• Always make small adjustments

• Wait between doses to allow water to stabilize

• Never add pH up and pH down at the same time

Using the right amount reduces the chances of overshooting or bounce-back.

Minimize Aeration And Bubbles

• Lower jet speed or limit aeration cycles

• Use air blowers less often

• Cover the hot tub when not in use to reduce CO2 loss

Cutting back on unnecessary aeration helps maintain pH without extra chemicals.

Shower Before Entering The Tub

Body care products like sunscreen, lotion, and hair gel affect water balance. Rinse off before soaking and ask guests to do the same.

What Products Help Control Rising pH?

To keep pH in check, use products designed for balance and prevention:

• pH decreaser (sodium bisulfate)

• Alkalinity reducers

• Pre-filters or water softeners

• Weekly maintenance balancers

• Enzymes to reduce organic buildup

Using these consistently can slow pH rise and reduce chemical demand.

When Should I Call For Help?

Sometimes rising pH is a symptom of deeper issues. Ask for help if:

• You lower pH and it rises again within a day

• Water feels rough or cloudy even after balancing

• You see white crust (scale) forming on surfaces

• Sanitizer stops working properly

A pool and spa professional can test for hidden imbalances and help identify long-term solutions.

How Do I Keep My pH Stable Over Time?

1. Test 2 to 3 times weekly

2. Adjust alkalinity before adjusting pH

3. Avoid overuse of jets and blowers

4. Add chemicals gradually and retest

5. Clean filters and maintain water circulation

6. Rinse off before using the tub

7. Drain and refill your hot tub every 3 to 4 months

By keeping up with these habits, you’ll enjoy clear, comfortable water without constant corrections.

Understanding the cause of rising pH is the first step toward regaining control. Once you identify the source, your hot tub becomes easier to maintain and more enjoyable to use.